Speedup processResources

[koppor]

processResources task was very slow:

$ gradlew processResources
> Configure project :
Project : => 'org.jabref' Java module

Deprecated Gradle features were used in this build, making it incompatible with Gradle 7.0.
Use '--warning-mode all' to show the individual deprecation warnings.
See https://docs.gradle.org/6.5/userguide/command_line_interface.html#sec:command_line_warnings

BUILD SUCCESSFUL in 49s
1 actionable task: 1 executed

Speed up by:

1. Pointing to the files to be modified directly
2. Add gradle file system watcher

@ C:\git-repositories\jabref\jabref
$ gradlew --watch-fs -Dorg.gradle.vfs.verbose=true processResources
Watching the file system is an incubating feature.
Received 7 file system events since last build
Virtual file system retained information about 21136 files, 269 directories and 1 missing files since last build

> Configure project :
Project : => 'org.jabref' Java module

Deprecated Gradle features were used in this build, making it incompatible with Gradle 7.0.
Use '--warning-mode all' to show the individual deprecation warnings.
See https://docs.gradle.org/6.5/userguide/command_line_interface.html#sec:command_line_warnings

BUILD SUCCESSFUL in 4s
1 actionable task: 1 up-to-date
Received 11 file system events for current build
Virtual file system retains information about 21136 files, 269 directories and 1 missing files till next build

• Change in CHANGELOG.md described (if applicable)
• Tests created for changes (if applicable)
• Manually tested changed features in running JabRef (always required)
• Screenshots added in PR description (for UI changes)
• Checked documentation: Is the information available and up to date? If not created an issue at https://github.com/JabRef/user-documentation/issues or, even better, submitted a pull request to the documentation repository.