Consider renaming the module, spelling dir in lowercase

[scop]

For the same reasoning as in #30, consider renaming the module directory to just upcloud. In addition to the "VPS" consideration, all other directories in WHMCS modules/servers/ are spelled in all lowercase too.

Consider also removing Vps from filenames within the dir, and making corresponding adjustments wherever needed

• ./upCloudVps.php
• ./lib/upCloudVps.php
• ./templates/assets/img/vps-details.png

[scop]

The "upCloudVps" name has ended up in the databases of some existing setups, and changing it would require migrations. This is not deemed worth it, so we'll leave the name as is.

[adityawbwce]

Based on @scop comment we can close this issue