New configuration option wgFlowServerCompileTemplates

By default templates will not be recompiled, but within a developers
environment they may want to force recompilation.  This pushes that
decision out into a new top level config variable. A full force is used
rather than checking mtime to keep everything simple, compilation
doesn't take particularly long.

The patch at Ifb7908db62d558e1a7fa334e818d66d3c03e8a30 sets this to
a default of true within the mediawiki-vagrant development environment

Change-Id: I6dac2795c59d644f599eaafe947b0b22b1253119
Merge "New configuration option wgFlowServerCompileTemplates" into frontend-rewrite