Add/update LEM footprints

For https://github.com/KiCad/kicad-symbols/pull/615 I reviewed some LEM footprints. Seeing how awful they were I went ahead and spent time on all non-Allegro and non-AKM footprints in this library.

LEM_HO-NP

• Updated descriptions
• Wrong pin placement and number of pins! (It seems to be a copy of the item below)
• Some dimensions guessed since no 3D model is available.
• Update datasheet to https://www.lem.com/sites/default/files/products_datasheets/ho-np_0100__1100_series.pdf

LEM_HO-NP_SP33

• Replace underscore within footprint name with hyphen
• Updated descriptions
• Should it be named LEM_HO-NP-SP33 (hyphen before "SP33") since the underscore usually moves to a new section of the footprint name?
• Did not capture the thinner part of the body near pins 8-13
• Update datasheet to https://www.lem.com/sites/default/files/products_datasheets/ho-np_sp33-1000_series.pdf

LEM_HTFS

• Near-total redesign to match datasheet dimensions and add fab lines
• Fix silk line width to 0.12mm and fab line width to 0.1mm
• Avoid silk under part body
• Add datasheet of https://www.lem.com/sites/default/files/products_datasheets/htfs_200_800-p_sp2.pdf

HX*_HallEffectCurrentTransducer

• Remove _HallEffectCurrentTransducer from footprint name
• Add LEM_ to footprint name
• Correct dimensions per datasheet
• All silk lines to 0.12mm
• Add/separate footprints where pin sizes differ and by MPN
• Note: HX 50-P/SP2 kept rather large pads from existing footprint
• Updated datasheets

LEM_LA25-P

• Rename footprint to accomodate all LA variants
• Moved pins to correct Y position
• Moved fab value to inside part body
• Avoid silk under part body
• Make pin 1 silk mark equal X and Y value from fab lines
• Update datasheet to https://www.lem.com/sites/default/files/products_datasheets/la_25-p.pdf

LEM_LV25-P

• Set pad drill size to match datasheet for pins 4-6
• No drill size is given for pin 1 and 3, but made them the same oversize from the pin diameter as pins 4-6
• Moved fab value to inside part body
• Make pin 1 silk mark equal X and Y value from fab lines
• Minor correct to bottom courtyard line location
• Update datasheet to https://www.lem.com/sites/default/files/products_datasheets/lv_25-p.pdf

Dimensions not provided were taken from manufacturer's 3D models. Some dimensions were not specified and may fall outside the nominal range but were kept on the assumption that these dimensions were originally taken from measuring an actual component.

I realize there is a lot here, so please feel free to check things out in detail if you want or just quickly scanning through it to get the fixes merged faster.

Images (old on left and new on right; only a smattering of the HX* footprints shown):

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Thanks for creating a pull request to contribute to the KiCad libraries! To speed up integration of your PR, please check the following items:

• Provide a URL to a datasheet for the footprint(s) you are contributing
• An example screenshot image is very helpful
• If there are matching symbol or 3D model pull requests, provide link(s) as appropriate
• Check the output of the Travis automated check scripts - fix any errors as required