Allow compilation of arbitrary values from files

Currently I can compile values, lambdas, etc. using something like ligo compile-expression cameligo "fun (a : nat) -> a + a". However this doesn't seem to work in more complex scenarios because #include is not supported in this context.

If I have a file called MyFile.mligo

#include "MoreDefinitions.mligo"

let myValue = fun (a : nat) -> a + a

And try to compile myValue with

ligo compile-expression cameligo "
#include \"MyFile.mligo\"
myValue
"

It attempts to compile, but the compiler is trying to evaluate the whole input as a value and fails.

It would be helpful if I could write something like ligo compile-expression MyFile.mligo myValue (similarly to evaluate-value).

Some use cases for this:

• gas optimization scenarios involving storing lambdas in big_maps (compiling arbitrary lambdas would be possible)
• admin entrypoint accepting arbitrary lambdas for execution (again, I could write my admin lambdas in Ligo)
• TZIP-16 is proposing off-chain Michelson views - off-chain views could be written using Ligo