doc: Reformat MCA section and add a quickstart for runtime tuning

This reformats the MCA section to be more inline with the rest
of the sections. It also adds a quickstart section for easier
user visibility of setting MCA parameters.

Signed-off-by: William Zhang <wilzhang@amazon.com>

Author: wckzhang

docs/Makefile.am

@@ -38,6 +38,7 @@ RST_SOURCE_FILES   = \
         $(srcdir)/release-notes/*.rst \
         $(srcdir)/installing-open-mpi/*.rst \
         $(srcdir)/installing-open-mpi/*/*.rst \
+        $(srcdir)/mca/*.rst \
         $(srcdir)/features/*.rst \
         $(srcdir)/building-apps/*.rst \
         $(srcdir)/launching-apps/*.rst \

docs/index.rst

@@ -64,10 +64,10 @@ Table of contents
    getting-help
    release-notes/index
    installing-open-mpi/index
+   mca/index
    features/index
    validate
    version-numbering
-   mca
    building-apps/index
    launching-apps/index
    tuning-apps/index