Properly update 'wasmoved' variable for plot markers.
Properly update 'wasmoved' variable for plot markers.

Markers not added via click weren't getting attach to the default drag
handler which is responsible for setting up the movement boolean

Partially Fixes #576

RickMohr/otm-core,clever-crow-consulting/otm-core,recklessromeo/otm-core,maurizi/otm-core,recklessromeo/otm-core,maurizi/otm-core,RickMohr/otm-core,recklessromeo/otm-core,clever-crow-consulting/otm-core,recklessromeo/otm-core,RickMohr/otm-core,RickMohr/otm-core,clever-crow-consulting/otm-core,maurizi/otm-core,clever-crow-consulting/otm-core,maurizi/otm-core