Don't re-register FileChangeListener on setup.py

This avoids the update time to grow longer and longer each time setup.py is updated.

#257461: Force UTF-8 encoding in setup.py if getting properties failed

This can happen when opening Python 3 projects since encoding is UTF-8 by
default, which means setup.py may not contain the the encoding line.

To do this, when getting the properties, we:
- copy the setup.py file
- append the encoding line at the beginning
- get the properties and detele the file

#181102 Set encoding in templates

Based on a contribution by vincentvdl[at]netbeans.org

Improve source level detection

Source can level can be of type X.Y instead of Python.X.Y

Don't try to add non Python interpreter as Python platform

In PythonPlatformManager, if the commands succeed but is not a Python interpreter
its name will be null (eg /usr/bin/ls). This will cause subsequent call to
"Manage" to fail due to a NullPtrException. We prevent this by returning a null
platform if the name is null.

This can happen if the user enters a wrong path when registering a new Python
platform.

#267313 Don't report NullPtrExcep in PythonParser.standardParse

Log them instead.

Improve auto detection of Python on linux

- Correctly detects all Python executable in /usr/bin (including Python 3 and
Python 2)
- Detects Pypy

#267333 Prevent NullPointerException if no platform is defined for project

In PythonProjectSourceLevelQuery.findValue we relied on the platform for the project but it may not be defined. In this case, we use the default platfrom instead.

Added tag release82_base for changeset 04a79821e760

The release82 branch created.