Adds repipe="" and disable="" attributes to PipedExecBuilder
- it allows to change a pipe created in pre-configured pipedexec plugin

Fix in pipedexec's exec properties setting
- if no workingdor was set, it was set to a default value in ExecBuilder#validate()
- therefore, pipedexec was unable to detect that workingdir was not set
- moving the setting to #validate() (where it should be anyway) fixed the problem
- other properties are handled in the same way

Fix in project files reading (seems as regression from 2.8.4):
- absolute path to project file worked in 2.8.4
- path relative to main config file was expected now
- the change checks if the path is accessible from the current directory and uses it if so, or expects path relative to main config file (as before)


git-svn-id: https://cruisecontrol.svn.sourceforge.net/svnroot/cruisecontrol/trunk/cruisecontrol@4623 878de816-9c12-0410-b5fe-b34e1928e20d
Environment (<env/> tag) configuration is handled by PipedExecBuilder as well
Fix inf loop in Builder#mergeEnv() when ${ENVVAR} is referenced but not defined in the ENVs (tests stressing mergeEnv() added to BuilderTest)

Few typo fixes in documentation

git-svn-id: https://cruisecontrol.svn.sourceforge.net/svnroot/cruisecontrol/trunk/cruisecontrol@4624 878de816-9c12-0410-b5fe-b34e1928e20d
fix of build failure

git-svn-id: https://cruisecontrol.svn.sourceforge.net/svnroot/cruisecontrol/trunk/cruisecontrol@4625 878de816-9c12-0410-b5fe-b34e1928e20d
Revert of accident commit. Sorry about this

git-svn-id: https://cruisecontrol.svn.sourceforge.net/svnroot/cruisecontrol/trunk/cruisecontrol@4626 878de816-9c12-0410-b5fe-b34e1928e20d
Added inherits="" attribute to <plugin/> configuration, allowing simple hierarchical plugins congiguration.

git-svn-id: https://cruisecontrol.svn.sourceforge.net/svnroot/cruisecontrol/trunk/cruisecontrol@4627 878de816-9c12-0410-b5fe-b34e1928e20d