…mplate.

- `${year}`: The current year with century as a decimal number.
- `${month}`: The current month as a decimal number [01,12].
- `${monthname}`: The current month's (local) name.
- `${day}`: The current day of the month as decimal number [01,31].

The new `plugin.py` imports `datetime`, so we use it.

IMPORTANT: When backporting, add `from datetime import datetime`!

…le template.

We now have the following variables, which can be used in the new file
template:
- `${date}`: The date and time without timezone information.
- `{$isodate}`: The date and time in ISO format (including timezone
information).
- `${year}`: The current year with century as a decimal number
[0001,9999].
- `${month}`: The current month as a zero-padded decimal number [01,12].
- `${day}`: The current day of the month as zero-padded decimal number
[01,31].
- `${hour}`: The current hour (24-hour clock) as a zero-padded decimal
number [00,23].
- `${minute}`: The current minute as a zero-padded decimal number
[00,59].
- `${second}`: The current second as a zero-padded decimal number
[00,59].
- `${tzname}`: The local time zone name.
- `${monthname}`: The current month as locale's abbreviated name.
- `${weekday}`: The current weekday as locale's abbreviated name.

…he new file template.

Information, how this can be done on Windows, are taken from
https://sjohannes.wordpress.com/2010/06/19/win32-python-getting-users-display-name-using-ctypes/.

Uses the OS name instead of trying to receive the 'USERNAME' environment
variable, which is only available on Windows.

…on of the new file name.

This is needed, so that we can include a filename and filepath variable
to be used in the new file template.

… the new file template.

New template variables:
- `${file}` - The full file name including the path.
- `${filename}` - The file name.
- `${filepath}` - The file path.

… in the new file template.

New template variables:
- `${projectname}` - The project name.
- `${projectpath}` - The project directory.

The first occurance of the marker `$|$` is removed from the template and
the cursor positioned in that place.