metrics: make tf metrics configurable for x,y,z,r,p,y

[floweisshardt]

it should be possible to configure the tf_length_X-metrics to only take translation/rotation around x axis into account.

Possible configuration examples are:

tf_length_translation/tf_distance_translation:

• default: calculate for all axes (x, y, z in root_frame)
• xyz: same as default
• x: only calculate for x
• y: only calculate for y
• z: only calculate for z
• xz: only calculate for x and z

tf_length_rotation/tf_distance_rotation:

• default: calculate for all axes (roll, pitch, yaw in root_frame)
• xyz: same as default
• x: only calculate for roll
• y: only calculate for pitch
• z: only calculate for yaw
• xz: only calculate for roll and yaw

[fmessmer]

why not use some kind of "bitmask"?
i.e. bit 0 stands for x, bit 1 stands for y and bit 2 stands for z?
3 = 011 -> xy
5 = 101 -> xz
etc...