Generics

[burrbull]

r? @therealprof
cc @adamgreig

I did it. Almost.

But still have problems with naming.

I want to name field enum as FIELD. But in some cases this cause troubles.

Now such system:

• _R and _W for registers readers/writers (better R and W as it was before, but conflicts with field W)
• FIELD for field enums/structs.
• FIELD_R - field reader (was FIELDR before): now conflicts with CLK_EN_R field on Fujitsu and Spansion targets.
• FIELD_W - field writer (was _FIELDW + FIELDW if have enumerated values)

[therealprof]

@burrbull You're too quick for me. Why did you close this? 😅

[burrbull]

I found one bug in write proxy (tha. They shall not be derived (type FIELD_W<'a> = BASEFIELD_W<'a>) if base enum is out of register.
It should be new type FIELD_W<'a> = WProxy<'a, u32, REGNAME, bool, BASEFIELD, crate::Safe>.
Otherwise it will create incorrect register writers.

I thought I fix all main issues and create this common PR.
I can reopen #331 until find solution.

Also, there is a problem with names.