FLUID-5327: Converting ChangeApplier doc

Converted http://wiki.fluidproject.org/display/docs/ChangeApplier+API to a markdown page.
FLUID-5327: Change syntax for italics

Using _ instead of * for italics to avoid conflicts and confusion with ** for bold.
Merge branch 'master' into FLUID-5327
FLUID-5327: Updated based on code review.

Added more inline codifying.
Merge branch 'master' into FLUID-5327