Migrated svnexternals.txt file operations to a separate class.

Signed-off-by: Oleg Nenashev <nenashev@synopsys.com>
[FIXED JENKINS-15098] - Added synchronization of all reads/modifications of svnexternals.txt file.

Resolves https://issues.jenkins-ci.org/browse/JENKINS-15098

Signed-off-by: Oleg Nenashev <nenashev@synopsys.com>
[JENKINS-15098] - Refactoring
Moved base class to another package, modified visibility and javadoc.

Related issues: https://issues.jenkins-ci.org/browse/JENKINS-15098

Signed-off-by: Oleg Nenashev <nenashev@synopsys.com>
Removed CacheItem, added javax annotations to SvnExternalsFileManager

Signed-off-by: Oleg Nenashev <o.v.nenashev@gmail.com>
Revert "Fix JENKINS-18574"

This reverts commit fe0b64105c2a585831e0cac90587ccd582c4c838.
Revert "merge JENKINS-18574 branch"

This reverts commit ec606ac7557772cb07e72f00c084203810ebd815, reversing
changes made to 3f09b1c6c0402235e1e4b8719a134f49d9c40766.

Conflicts:
	src/main/java/hudson/scm/SubversionChangeLogBuilder.java
JENKINS-22742 : Be sure that file paths used in tests are plateform-independant.
Merge pull request #78 from daniel-beck/JENKINS-22778

[FIXED JENKINS-22778] Revert JENKINS-18574 related changes
Merge pull request #79 from flesire/JENKINS-22742

JENKINS-22742 : Make sure that file paths used in tests are platform-independent
Use maven-release-plugin 2.5 which fixes
http://jira.codehaus.org/browse/SCM-686
[maven-release-plugin] prepare release subversion-2.3
[maven-release-plugin] prepare for next development iteration
Merge pull request #65 from synopsys-arc-oss/externalsfile-conflicts

[FIXED JENKINS-15098] - Access conflicts to svnexternals.txt