DOC-ONLY: build system details

The tables need some TLC from someone familiar with making pretty
tables.

Fixed text-wrapping onto newlines for all tables in our docs.
Changed Environment Variables to ENV Variables so that the specific
column header fits properly.

Change-Id: Ie758612e561eefe44e771dac63b63bf026a52c2d
Signed-off-by: Dave Barach <dave@barachs.net>

docs/_static/css/rules.css

@@ -1,5 +1,19 @@
+/* Allows for tables to be center-aligned */
 table.center-align-table td {
     text-align: center;
 }
 
+/* override table width restrictions */
+@media screen and (min-width: 767px) {
+
+   .wy-table-responsive table td {
+      /* !important prevents the common CSS stylesheets from overriding
+         this as on RTD they are loaded after this stylesheet */
+      white-space: normal !important;
+   }
+
+   .wy-table-responsive {
+      overflow: visible !important;
+   }
+}
 

docs/reference/buildsystem/index.rst

@@ -0,0 +1,11 @@
+.. _buildsystem:
+
+Build System
+============
+
+This reference guide describes the vpp build system in detail
+
+.. toctree::
+
+    mainmakefile
+    buildrootmakefile

docs/reference/buildsystem/mainmakefile.md

@@ -0,0 +1,3 @@
+Introduction to the top-level Makefile
+======================================
+

docs/reference/index.rst

@@ -8,3 +8,4 @@ Reference
 
    vppvagrant/index.rst
    cmdreference/index.rst
+   buildsystem/index.rst