Include CRS axis units in CRS routes

[kbevers]

Example of response:

{
    "area_of_use": "Europe between 6\u00b0E and 12\u00b0E: Austria; Belgium; Denmark - onshore and offshore; Germany - onshore and offshore; Norway including - onshore and offshore; Spain - offshore.",
    "bounding_box": [
        6.0,
        38.76,
        12.0,
        84.33
    ],
    "country": "DK",
    "srid": "EPSG:25832",
    "title": "ETRS89 / UTM Zone 32 Nord",
    "title_short": "ETRS89/UTM32N",
    "v1": "Easting",
    "v1_short": "x",
    "v1_unit": "metre",
    "v2": "Northing",
    "v2_short": "y",
    "v2_unit": "metre",
    "v3": "Ellipsoideh\u00f8jde",
    "v3_short": "h",
    "v3_unit": null,
    "v4": null,
    "v4_short": null,
    "v4_unit": null
}

The data response from /v1.2/crs/ is now sorted by it's keys for better human readability.

Closes #43

[coveralls]

Pull Request Test Coverage Report for Build 2677597823

• 46 of 48 (95.83%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.08%) to 95.014%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
tests/test_api.py	21	22	95.45%
webproj/api.py	25	26	96.15%
<!--	Total:	46	48	95.83%	-->

Totals
Change from base Build 2550589912:	0.08%
Covered Lines:	343
Relevant Lines:	361

---

💛 - Coveralls