Update for Houdini 18

Release 7.1.2

1. Updated for Houdini 18.

2. New expression functions added:

    string abspath(string relpath)
    string decodeattrib(string s)
    string decodeparm(string s)
    string encodeattrib(string s)
    string encodeparm(string s)
    string lopparentprims(string lop_paths)
    string loprelativeprims(string lop_paths, string relative_path)
    string opinputstring(string name, float index, string key)
    string pdgattribute(string name, float index)
    string pdgattributes(string name, float index)
    string pdginput(float index, string tag, float localize)
    string pdgoutput(float index, string tag, float localize)
    string relpath(string abspath)
    float scalefrommks(string dimensions)
    float scaletomks(string dimensions)

    Tip: to read about new functions quickly, copy the list in empty
    Sublime Text document, set HScript syntax and check documentation helpcards.

3. Commands highlighted in syntax:

    ociocolorspace
    ociodisplay
    scenegraphtree
    sceneviewopts
    sceneviewpurpose
    sceneviewrenderopts
    topcancel
    topcook
    topdirty
    visualizeradd
    visualizerset