Refactor delete in context menu to show individual labels

Implement additional feature requested in #41.

Change-Id: Ibf4e102c89fa5e20bbc097b6b500124aa59d352d
Signed-off-by: Denis Knoepfle <denis.knoepfle@sap.com>
Update plugin information, names and tooltips

Updated plugin name in plugin.xml and pom.xml to 'DynamicSpotter Eclipse
UI' and added vendor 'SAP AG'.
Fixed some outdated descriptions and tooltips for commands.

Change-Id: If4ec64d5a3c7eb1a1d0888b5e84e0bcc7746bc3a
Signed-off-by: Denis Knoepfle <denis.knoepfle@sap.com>
Implement clear cache feature (issue #57)

Implemented the feature and made it available in the context menu when
at least one project is selected. Currently there is a bug when
right-clicking on the project which has not been selected before. This
problem is addressed in #63.

Change-Id: Ic4c9cc663c06f9d49532f370789dbd762c3d8789
Signed-off-by: Denis Knoepfle <denis.knoepfle@sap.com>
Add info message when no extension available (issue #58)

Changed the button to show an error message when there is no connection
to DS Service and an information message when zero extensions could be
retrieved. The path displayed in the message dialog may be adjusted
later.

Change-Id: I2082c2545bd023418ffbec14f09260fdd5fa2686
Signed-off-by: Denis Knoepfle <denis.knoepfle@sap.com>