small cleanup
added single eunit test run capability;
refactored runconfig-related classes; modified eunit runconfig (added option which allows to run tests on selected functions or selected modules);
added 'rerun failed tests' action;
added 'run selected test files' capability; added tests for it;
added Rebar Eunit tests run configuration (with capability to run single or multiple tests and/or test suites);
fixed navigation from tests results to code; cleaned up code; fixed test console bug which led to incorrect test result representation;
added 'rerun failed tests' action for rebar run configuration;
added tests for eunit test events converter;
reimplemented unit test events converter; added tests for nested module tests;
changed rebar eunit run configuration default parameters; removed 'use test console' option;
modified rebar rerun failed tests action: added notification on generated tests fail; changed activation policy - the action is now active if any of tests have failed;