This commit reinstates the Spring Framework BOM, which was previously
empty because of a previous change in 41cbc4670f.
This change also removes the JSR305 dependency from the BOM, which does
not belong here since it is not an artifact produced by Spring.
Issue: SPR-15885
The main `build.gradle` file contains now only the common build
infrastructure; all module-specific build configurations have
been moved to their own build file.
Issue: SPR-15885
Stephane Nicoll
Juergen Hoeller
Brian Clozel
Paul Verest
Phillip Webb