Version Control Environment & Status Check Flag

These changes were suggested due to slow git status and environment checks within themes. Users can now opt out of all generic version control environment checks. 

Themes that utilize specific version control environment check functions like **git_prompt_vars**, in order to populate prompt variables, are not affected by this change. 

themes/base.theme.bash
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* Added a flag **SCM_CHECK** that controls if themes should display version control environment and status within the bash prompt. 
   * If **SCM_CHECK** is false, then the base theme will skip checks to version control characters, variables, and general info. 
   * If **SCM_CHECK** is true, then the base will not skip checking of version control characters, variables, and general info.
   * **SCM_CHECK** is true by default in order to allow for previous themes to behave as normal.
   * Users must manually opt out of version control checks. 

template/bash_profile.template.bash
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*  Added the **SCM_CHECK** version control check flag to the bash_profile template.
   * This will allow users to easily change the value of the flag without needing to dig into the base theme.