update Debian files, remove Python bytecode

Fixes the following Lintian tags:
```
W: mintinstall source: debhelper-but-no-misc-depends mintinstall
W: mintinstall source: debian-rules-missing-recommended-target build-indep
W: mintinstall source: debian-rules-missing-recommended-target build-arch
W: mintinstall source: binary-arch-rules-but-pkg-is-arch-indep
W: mintinstall source: ancient-standards-version 3.7.2 (current is 3.9.5)
E: mintinstall: package-installs-python-bytecode usr/lib/linuxmint/mintInstall/widgets/__init__.pyc
E: mintinstall: package-installs-python-bytecode usr/lib/linuxmint/mintInstall/widgets/pathbar2.pyc
E: mintinstall: package-installs-python-bytecode usr/lib/linuxmint/mintInstall/widgets/rgb.pyc
E: mintinstall: package-installs-python-bytecode usr/lib/linuxmint/mintInstall/widgets/searchentry.pyc
W: mintinstall: debian-changelog-line-too-long line 6
W: mintinstall: copyright-without-copyright-notice
E: mintinstall: package-installs-python-bytecode usr/lib/linuxmint/mintInstall/Classes.pyc
```