Fixed some Dialyzer issues.

Removed some apps from the build_plt Makefile target to speed up Dialyzer PLT generation.

Change the PLT-related Makefile targets to depend on all. Dialyzer needs the dependencies in place to generate PLTs.

Added {search_index, binary()} to the -spec for server_prop. This property describes a Yokozuna index. This gets rid of Dialyzer warning.
Merge pull request #141 from NineFX/dialyzer-fixes

Fixed some Dialyzer issues.