Fix editor's range specification

[chiizujin]

Brief overview of PR changes/additions

The editor's range specification (n:n) returns at most two lines. This has been fixed.

Also, as part of this:

• An existing unit test has been corrected
• New unit tests have been added to test various ranges
• utils.value_is_integer(value) has been added which returns True if value can be type-cast to an integer and False otherwise. This is to allow checking for negative integers, which str.isdigit() can't do.

Motivation for adding to Evennia

Fix editor range specification.

Other info

Test buffer

>:
----------Line Editor [desc]--------------------------------------------------
01| line 1
02| line 2
03| line 3
04| line 4
05| line 5
----------[l:05 w:010 c:0034]------------(:h for help)------------------------

Before

>: 1:5
----------Line Editor [desc]--------------------------------------------------
01| line 1
02| line 2
----------[l:02 w:004 c:0013]------------(:h for help)------------------------

After

>: 1:5
----------Line Editor [desc]--------------------------------------------------
01| line 1
02| line 2
03| line 3
04| line 4
05| line 5
----------[l:05 w:010 c:0034]------------(:h for help)------------------------

Changed unit test

def test_eveditor_COLON_F(self):
    eveditor.EvEditor(self.char1)
    self.call(
        eveditor.CmdEditorGroup(),
        "",
        cmdstring=":",
        msg="Line Editor []\n01\n[l:01 w:000 c:0000](:h for help)",
    )
    self.call(eveditor.CmdLineInput(), "line 1", raw_string="line 1", msg="01line 1")
    self.call(eveditor.CmdEditorGroup(), "1:2", cmdstring=":f", msg="Flood filled lines 1-2.

This test expects the output "Flood filled lines 1-2." for a buffer containing only one line. After the fix the above command will return "Flood filled line 1.", which is correct. The test has been updated to look for the new output.

[Griatch]

This is fine, but in case you were not aware, you can also do try: ... except: ... else: ... in Python :)

[chiizujin]

I always forget about else in try blocks.

[Griatch]

This is good attention to detail. And looks like a clean fix supported by unit tests. Nice!