DOCS: Formatting and organization changes.

Additionally:

* Added an overview
* Expanded the docs for the NULL type.

docsite/site/content/reference/expressions.md

@@ -1,5 +1,5 @@
 +++
-title = "UCG Expressions"
+title = "Expressions"
 weight = 3
 sort_by = "weight"
 in_search_index = true

docsite/site/content/reference/grammar.md

@@ -1,5 +1,5 @@
 +++
-title = "UCG Formal Grammar"
+title = "Formal Grammar"
 slug = "grammar"
 weight = 1
 sort_by = "weight"

docsite/site/content/reference/overview.md

@@ -0,0 +1,30 @@
++++
+title = "Overview"
+slug = "overview"
+weight = 0
+sort_by = "weight"
+in_search_index = true
++++
+
+UCG is an expression oriented functional language with immutability,
+copy-on-write semantics and forward type inference. Everything in UCG is an
+expression except for a few statements that introduce named bindings or
+generate an output.
+
+UCG is purpose built for constructing configurations. Anything that is not
+useful for that is excluded. All ucg output targets one of the compilation
+conversion targets.
+
+UCG can import supported configuration formats and transform them before
+outputting them into one of the compilation conversion targets. UCG also has
+built in support test assertions in your configuration generation and
+transformation logic.
+
+Among the possibilities this opens up are:
+
+* Slowly migrating existing configuration formats over to UCG
+* Sharing common configuration values across static configurations
+* Enforcing invariants in your configurations at build time
+* Unit testing your configuration generation logic
+* Converting one config format to another config format
+* Dynammic querying of your configurations using the `ucg eval` command

docsite/site/content/reference/statements.md

@@ -1,5 +1,5 @@
 +++
-title = "UCG Statements"
+title = "Statements"
 weight = 4
 sort_by = "weight"
 in_search_index = true

docsite/site/content/reference/types.md

@@ -1,5 +1,5 @@
 +++
-title = "UCG types"
+title = "Types"
 weight = 2
 sort_by = "weight"
 in_search_index = true
@@ -50,7 +50,9 @@ Strings are any double quoted text. You can use the `\` to esacpe characters in
 ### NULL or the Empty type
 
 NULL is the empty type. It represents the absence of a value. It is represented by the
-symbol `NULL`.
+symbol `NULL`. The empty type is special in that any field regardless of type can be assigned
+the `NULL` value and any field of NULL value can be assigned any type. This is most useful when
+you need a module, tuple, or function to have fields or parameters that can be any type.
 
 ```
 let empty = NULL;

docsite/site/content/stdlib/functional.md

@@ -1,5 +1,5 @@
 +++
-title = "UCG functional operations"
+title = "Functional operations"
 weight = 5
 sort_by = "weight"
 in_search_index = true

docsite/site/content/stdlib/lists.md

@@ -1,5 +1,5 @@
 +++
-title = "UCG List Modules"
+title = "List Operations"
 weight = 1
 sort_by = "weight"
 in_search_index = true

docsite/site/content/stdlib/schema.md

@@ -1,5 +1,5 @@
 +++
-title = "UCG Schema Modules"
+title = "Schema Helpers"
 weight = 4
 sort_by = "weight"
 in_search_index = true

docsite/site/content/stdlib/testing.md

@@ -1,5 +1,5 @@
 +++
-title = "UCG Testing Modules"
+title = "Testing Helpers"
 weight = 3
 sort_by = "weight"
 in_search_index = true

docsite/site/content/stdlib/tuples.md

@@ -1,5 +1,5 @@
 +++
-title = "UCG Tuple Modules"
+title = "Tuple Operations"
 weight = 2
 sort_by = "weight"
 in_search_index = true