Currently, the compilation engine displays a
message in the output window for every compiler.
This is done in method
org.netbeans.api.compilation.Compiler.logTargetMessage().
This works well for the project build which uses
compilers as build targets, however it is not so
good for compilers which are used by non-build
actions. 

For example, file validation can be done using the
compiler API, but it is not a part of the build.
Here, Compiler should be seen just as an
implementation detail of no interest to the user.
So the message should be suppressed completely
(there is already the message which starts the
whole job, so an additional message is unnecessary).

This could be addressed either by making
logTargetMessage() protected, or by allowing null
as return value in Compiler.getDisplayName(), and
not displaying the message if display name is null. 


The there is a second issue. The compiler job can
provide its own start message, however the final
message is hardcoded to "Compilation
finished....". It would probably be more
appropriate to use "building" by default. And it
should also be override-able, to maintain symmetry
with the ability to override the start message.
The validate action would choose "Validation
finished...."