Added send, startmining and stopmining commands. Now, you can mining from wallet software. New commands usage:
send: send stlx_address stlx_amount
startmining: startmining number_of_threads.
stopmining: stopmining

Changed wallet generation algo from aes-256-cfb to aes-256-cbc.

requests.session used for better network performance.

Python 3.8 used to build it, instead 3.5 on latest versions to avoid some deprectaion messages.