(riparian rights of shoreline boundaries where property lines meet shoreline at right angles to be determined by straight extension method rather than right angle method; but trial court’s determination that plaintiff had not acquired titled to a portion of defendant’s lot via adverse possession reversed – trial court failed to determine whether defendant (or predecessors in interest) exerted sufficient control, intent, notice and duration over subject property, and trial court failed to consider whether plaintiff had reasonable belief that it had paid taxes on disputed strip).