Updated UI and added backspace button in Calculator App

[akashdnb]

Added backspace button in Calculator app

fixes #95

Added a backspace button
which will delete the last entered digit and will be convenient for users.

Changes:

• Removed the action bar which was not suitable on the calculator screen.
• Added backspace button to pop the input numbers
• Changed primary and secondary colors to suit the theme
• Fixed some other performance bugs

Type of Change:

• Updated exiting applications

Checklist:

• My PR follows the style guidelines of this project
• I have performed a self-review of my own code or materials
• My branch is up-to-date with the Upstream development branch
• I have added necessary images/screenshots of my changes

Screenshots

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[aadityamp01]

Hey @akashdnb
We don't accept PR without a issue linked to it, if you want to open PR please open a issue first and after assignment, you can do so!
Thank you!

[akashdnb]

Hey @akashdnb We don't accept PR without a issue linked to it, if you want to open PR please open a issue first and after assignment, you can do so! Thank you!

@aadityamp01 I have linked the issue which will be solved by this PR #95

[aadityamp01]

Hey @akashdnb
Thanks for your contribution into Androapps!