Fix moh reset button in fault tree editor

[kostobog]

@blcham
Fix #593

Fixes behavior of MOH input field and its refresh button.

The screen shots below show how the MOH input field is rendered based on three variables,

• value of field MOH (MOH),
• fault tree MOH (ftMoh ) and
• system MOH (sMOH).

The style of MOH field uses orange color for the value of the MOH filed to distinguish if MOH is different from sMOH and orange color to of the border of the field to distinguish if MOH different from ftMOH. The field also has localized hint(s) to show

1) MOH = ftMoh and MOH = sMOH

2) MOH != ftMoh and MOH != sMOH - e.g. user updated MOH the value in the field

3) MOH = ftMoh and MOH != sMOH - e.g. user evaluated tree with MOH != sMOH

4) MOH != ftMoh and MOH = sMOH - e.g. user updated MOH to be equal to sMOH

The reset button updates the MOH value. Note that the reset button does not persist MOH (i.e. does not set ftMOH by calling server api) and it does not evaluate fault tree with MOH. The reset button works as follows based on the current state MOH, ftMOH and sMOH:
1) MOH = ftMoh and MOH = sMOH

• do nothing
  2) MOH != ftMoh and MOH != sMOH or 4) MOH != ftMoh and MOH = sMOH
• MOH := ftMoh
  3) MOH = ftMoh and MOH != sMOH
• MOH := sMOH - sets MOH to sMOH

User