Do not escape slashes in images href URLs

Fixes #57
Merge pull request #64 from Lucas-C/master

Do not escape slashes in images href URLs
rewrite code to not have warnings about not defined indexes, variables,
or not being able to write files
Slashes unescaping seemed overcomplicated.
Merge pull request #65 from Aldarone/simple-unescaped-slashes

Slashes unescaping seemed overcomplicated.
Merge pull request #63 from bifek/thumbwarnings

quiesce warnings
rename config.php to config-default.php and include (new) config.php
that contains only settings that are different than default ones.
also add config.php to gitignore.

all this will make it easier for users to sync with repo.
simplify $_GET usage (move to beginning for easy escape if need be).
simplify orientation reading from big case to two small arrays.
Merge pull request #69 from bifek/configdefault

rename config.php to config-default.php
use built-in is_dir() function
Merge pull request #72 from bifek/functions

use built-in is_dir() function
Merge pull request #70 from bifek/cleangetvars

simplify $_GET usage (move to beginning for easy escape if need be).
simplify sanitize() function