Update Unitful.uparse()

[michikawa07]

1 default value of unit_context argument
Nevertheless, expanded pkg of Unitful.jl (i.e., UnitfulAtomic.jl) execute Unitful.register(), Unitful.uparse did not recognize these pkgs automatically (due to the defaut value of unit_context arg is Unitful only).
This commit modified this issue.

2 allowed_funcs
To enable parsing some strings such as "(1:10)m", I added :colon and :(:).

3 parsing macro call
To enable parsing some strings such as "u"m/s"" (unit string including @u_str macro), I added some code in uparse content

[jusack]

+1 for this change, I just spent way too long trying to figure out why the imported unit was not parsing, the error message of lookup_units also was not super helpful

[sostock]

1 default value of unit_context argument

IMO, this is a good change.

2 allowed_funcs
To enable parsing some strings such as "(1:10)m", I added :colon and :(:).

We could think about this, but I would rather keep the number of allowed functions small. If (1:3)m is allowed, why not [1,2,3]m? What’s so special about :?

3 parsing macro call
To enable parsing some strings such as "u"m/s"" (unit string including @u_str macro), I added some code in uparse content

I don’t see how this is useful. Where would a “nested” unit string appear?

[michikawa07]

Thank you for your feedback.

We could think about this, but I would rather keep the number of allowed functions small. If (1:3)m is allowed, why not [1,2,3]m? What’s so special about :?

Hmmm, that may be true. If uparse allows ":", it should also allow "[]", and then there are no limits.

I don’t see how this is useful. Where would a “nested” unit string appear?

Yes I want use the nested unit sting. When saving a number with units, it may be converted to a macro and then written out as a string.