Option to disable form validation and optional flag to mark form pristine after submit

Fixes & Improvements

1. Adding the flag bs-no-validation on form will disable the bootstrap angular validation on the form and fallback to HTML5 validation (if present)
2. Adding a flag bs-pristine-on-submit on form will change the form's state to pristine instead of submitted and will hide all the validations. This is helpful when a form is used multiple times (without page change) and we want to hide the validation after each successful submission.

Code diff: v1.0.3-1...v1.0.4