TEIIDDES-1697: Fixes tests as a consequence of further use of DotProj…

…ectUtils

* MockFileResource
* MockProject
 * Improve the sanity of these classes and implement enough methods for
   a fake project to be returned by any MockFileResource
 * By default, a temp file is instantiated (although not actually created)
   to represent the .project file and the project is set to both open and
   accessible.

* TestDotProjectUtil
 * Due to making the mock project accessible and open, a different path is
   taken by the code to check for the project's nature. Thus, the test
   must be slightly modified to correctly mirror the changes.