Remove hardcoded server startup scripts

[Vinod Kavinda]

Currently, the server startup scripts (wso2server.sh) has been hard-coded. Please parameterise this since WSO2 EI has a different startup script (integrator.sh). Better to have this controllable by the products.

[Chamila]

I believe @Vishanth is working on something similar.

[Dilan Ariyaratne]

Closing since this was already addressed by #31