Import Dependencies MVP

[AlejandroEsquivel]

User Stories to be satisfied

• As a covalent user I should be able to define pip dependencies with corresponding versions such that no manual dependency installations required on execution nodes
• As a covalent user I should be able to define bash dependencies which execute prior to electron execution

Issue Breakdown

Note: Definition of Done includes unit tests for each issue

Reference Planning doc: https://docs.google.com/document/d/1n6xlvZjWbRbwmINFJV9QQmY03tcVFBBgMUzngb6wu4k/edit#
Reference Discussion: #661

• Proposal of database schema changes
• Implement call_before & call_after hooks for electrons
• Create Bash Dependency class (extension of Dependency Class with common apply method)
• Create Import Dependency class for pip (extension of Dependency Class with common apply method)
• [Time permitting]Create Import Dependency class for conda (extension of Dependency Class with common apply method)

Other Notes

Order in which dependencies must be installed:

Env->Bash->Module->Conda->Pip->Call_before
*function*
Call_after

[santoshkumarradha]

Also please refer the GitHub discussion by @kessler-frost