#37 Out-of-date cached results displayed

[Ondrej Chylik]

Problem: The cache (metricsdb files or memory) may
contain out-of-date values, which are still being
presented to user.

Steps to reproduce:
- Create a java project named for example Project1.
- Create some class(es) in this project, enable and run
Metrics
- Delete the project from workspace and filesystem
- Create a new empty java project with the same name
- Open the Metrics view and select the project
Now you see the out-of-date results of metrics.
Furthermore you see them without having Metrics
enabled for the new project.

When a project is deleted, Metrics should drop the
related computed results.
Also do the same when the Metrics is disabled for a
project.
+ There may be more points where the cache needs to
be cleared or recomputed...