support for requirements.txt

[daimor]

Added check for existing file requirements.txt at the root of module, and if exists tries to install dependencies from it with pip command, only for load and install commands

resolves #307

Existing module for testing python-faker

USER>zpm "install python-faker"

[USER|python-faker]     Reload START (/usr/irissys/mgr/.modules/USER/python-faker/0.0.2/)
[USER|python-faker]     requirements.txt START
[USER|python-faker]     requirements.txt SUCCESS
[USER|python-faker]     Reload SUCCESS
[python-faker]  Module object refreshed.
[USER|python-faker]     Validate START
[USER|python-faker]     Validate SUCCESS
[USER|python-faker]     Compile START
[USER|python-faker]     Compile SUCCESS
[USER|python-faker]     Activate START
[USER|python-faker]     Configure START
[USER|python-faker]     Configure SUCCESS
[USER|python-faker]     Activate SUCCESS