Solve problem in activation scripts

[traversaro]

PR #27 added some activation scripts to solve problems described in #25 . There are some problems in this activation scripts:

• Major version of library is hardcoded
• Only sh (for Linux/macOS) and command prompt (for Windows) is supported

I plan to solve this issue, but before the idea is to improve a bit https://github.com/mamba-org/multisheller to provide the tools to easily implement this improvements.

[traversaro]

I plan to solve this issue, but before the idea is to improve a bit https://github.com/mamba-org/multisheller to provide the tools to easily implement this improvements.

With the improvements in mamba-org/multisheller#16 it should be relatively easy to implement an activation and deactivation msh script and generate the scripts for all the shell that we want to support.