[Bug, Move Package] Support case-insensitive file systems

[tzakian]

If you have a Move package with two modules (or any combination of Module/Script) that have the same name modulo-case (e.g., "set" and "Set"), then the resulting compiled package will be invalid.

This is due to the fact that we choose the filename based on the module/script name. On case-insensitive file systems this will lead to use overwriting one file (the one for e.g., "Set") with the other (e.g., "set").

We need to figure out a good way of supporting case-insensitive file systems and/or raising an error or warning to the user when they have module/script names that may trigger this issue.

[tzakian]

After some offline discussion the current plan to resolve this issue is to make it an error if you have modules/scripts that would cause issues on a case-insensitive filesystem (regardless of the file system you're currently on). While a bit restrictive we feel this is fine since:

• The solution is relatively straightforward and we can provide a good error message/help on what to do
• It maximizes reusability of Move packages by other people (e.g., someone develops a package that works on their Linux machine, but then I can't use their package on my Mac machine).