Support of multiple JavaHl Client Adapter versions

[StefanFranzWeiser]

Currently only Client Adapter 1.9.7 is available, i.e. it is not possible to use MergeProcessor when a newer or older version of SVN is installed on the machine.

MergeProcessor should support multiple Client Adapter versions and use the one required on the running machine.

Each Client Adapter version must be provided within an own plugin. During startup all available adapters are checked and the first matching one will be used.

[d-gs]

Maybe of interest for this ticket: from Subclipse 4.3 changelog, among other changes:

• Supports several JavaHL versions with a separate feature
• Support for SVNKit 1.9.x