added optional history; normalized variable names
added optional history; normalized variable names

I added the option to enable history in file browser mode. I changed the starting directory to a fixed directory. I found the old behavior not very intuitiv especially with enabled history. The old behavior can be restored easily. Additionally, I changed the variable names. Primarily, because the EDITOR variable could lead to a recursive call to EDITOR if xdg-open used this variable. Thus, I prefixed all the variables to create a new namespace for rofi. I am at most decent in bash scripting so don't expect to much, but it works for me and I thought it might be something others appreciate. I  hope it is of any use. :)
carnager/rofi,carnager/rofi,carnager/rofi