UpdateEl refactor + updates

[MartinKavik]

Resolves #370.
Resolves #365.
Resolves #128.

Changelog:

• [BREAKING] UpdateEl<T> changed to UpdateEl<Ms> and fn update(self, el: &mut T); to fn update_el(self, el: &mut El<Ms>);.
• Added trait UpdateElForIterator<Ms>.
• Added support for all Iterators, Option, u32, i32, usize, f64 and references in element creation macros.

[MartinKavik]

cc @TatriX @rebo

[rebo]

Code read through looks good. Covers all latest issues.

I need to test but what is the error if a user doesn't use a reference in say &model.title which is now needed as this will be a common user error.

I assume rust suggests adding the & so all good.

[MartinKavik]

There were missing impl for String. See old code for comments about it - before this PR, all Strings were coerced into &str, so it provided some user comfort, but it deviated from the other entities and also it always cloned given String (String => &str => String). Maybe I should add it to change log as a breaking change.

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On Sat, 29 Feb 2020 at 13:46, rebo ***@***.***> wrote: Code read through looks good. Covers all latest issues. I need to test but what is the error if a user doesn't use a reference in say &model.title which is now needed as this will be a common user error. I assume rust suggests adding the & so all good. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#373?email_source=notifications&email_token=AENI3GVCBUO6F2CL5E2AAO3RFEBRPA5CNFSM4K44DAS2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOENLZGPI#issuecomment-592941885>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AENI3GSLLPCFJXSXQFEYZJTRFEBRPANCNFSM4K44DASQ> .

[rebo]

Yep I think it's definitely needed just have to manage the expected compiler errors when users try without a reference.