Print reserved keywords in bliss shell when used in a string.

In the bliss shell all the python reserved keywords appear in green even when used in a private string.

Example:

 BM29 [1]: vfilter
  Out [1]:    LABEL   DESCRIPTION         MOTOR POSITION(S)
           *  refpos  Reference position  vfilter_mot: 1.000  (± 0.010)
              yellow  Yellow filter       vfilter_mot: 2.000  (± 0.010)
              blue    Blue filter         vfilter_mot: 3.000  (± 0.010)
              empty   Empty hole          vfilter_mot: 4.000  (± 0.010)
the word filter appears in green, which is misleading.
BM29 [2]: print("visible filter")

In this example print is red, filter is green and visible is black, while filter should be black.