New session_context argument for TM1Service, RESTService

[MariusWirtz]

New optional parameter for TM1Service session_context, that controls what is displayed in the session column in Arc / Pulse / TM1top. Default value is "TM1py".
Default Can be overwritten as follows:

import configparser

from TM1py.Services import TM1Service

config = configparser.ConfigParser()
config.read('..\config.ini')

APP_NAME = "My TM1py Application"

with TM1Service(**config['tm1srv01'], session_context=APP_NAME) as tm1:
    dimensions = tm1.dimensions.get_all_names()
    for dim in dimensions:
        print(dim)

Resolves #59

[rclapp]

Excellent, this is exactly what we need.