Exclude browser extensions for password managers

Paste tries to detect confidential data by special markers that most of the password managers leave in the clipboard (it follows the nspasteboard.org convention). However, some of the password managers don’t provide the required information and Paste is not able to filter out the data copied from them.

So far the known cases are:

• LastPass browser extension (reported)
• 1Password X (please use the official 1Password classic extension instead)