Widget: Replace warning symbol with strikethrough

[walles]

Part of fixing #610.

On my phone, the account-disabled warning symbol in the widget is a bit outside of the widget and almost invisible.

Strikethrough is fine though, so this change replaces the warning icon in the widget with overstriking the balance if updates have been disabled for the account.

Also, in accordance with the Boy Scout Rule, this change fixes some warnings in BankdroidWidgetProvider.java and re-enables one Lint rule and one PMD rule.

[walles]

[goober]

The idea looks good and I will go through the code a bit later. In the mean time could you just verify how it looks when you have enabled the blur widget feature?

[walles]

[goober]

Thanks!