Add extended types for LineString

[gbroccolo]

As made for Point type, the PR contains the definitions of the extended geometries for LineString type.

Here basics methods for the new types have been defined, basically to reduce the extradimensions to 2D objectsin order to be integrated with the rest of the repo; e.g. LineStringZMS type is the most complete one, defining a linestring of 3+1D points in a given reference), and there's a method which reduces it to a LineStringZM which can be reduced as well to a simple LineString.

[coveralls]

Pull Request Test Coverage Report for Build 492

• 79 of 121 (65.29%) changed or added relevant lines in 14 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.003%) to 55.466%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
line_stringms.go	8	11	72.73%
line_strings.go	8	11	72.73%
line_stringzms.go	8	11	72.73%
line_stringzs.go	8	11	72.73%
line_stringm.go	7	17	41.18%
line_stringz.go	7	17	41.18%
line_stringzm.go	7	17	41.18%

Totals
Change from base Build 490:	0.003%
Covered Lines:	6307
Relevant Lines:	11371

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💛 - Coveralls

[gdey]

LGTM, but could you run go fmt on this.

Thank you.

[gbroccolo]

LGTM, but could you run go fmt on this.

Thank you.

Hi @gdey I formatted the code with go fmt, it also fixed the code of the previous PR for point type.

[gdey]

LGTM